The present invention is related in general to the field of semiconductor devices and methods, and more specifically to integrated circuits and methods of fabrication and operation comprising an information unit with permanent coding for wireless tagging.
Semiconductor chips have suffered, on a global scale, a steep increase of illegal use or outright theft in the last few years. Thefts are now occurring more at distribution and shipping centers rather than at factories. Worldwide losses of electronic components thefts are estimated at $8 billion per year, with the average theft typically resulting in a $750,000 loss (Dallas Morning News, Jan. 5, 1998, after Electronic News). According to Central News Agency, Taiwan, Feb. 26, 1998, a semiconductor company in Taoyuan County, Taiwan, was robbed of more than 3 million computer memory chips, worth more than $20 Million.
It would be a tremendous crime deterrent if each semiconductor chip could be permanently marked for recording producer, date of production, country of origin, and possibly fabrication history and performance characteristics. Unfortunately, known technology does not offer this capability. What is available, are discrete semiconductor devices for attachment onto larger objects for registration and identification purposes. For instance, semiconductor devices are produced which make it possible to identify or detect their presence in objects which are provided with such devices; the detection can be accomplished in contactless manner and over certain distances. As an example, U.S. Pat. No. 5,053,774 of Oct. 1, 1991 (Schuermann et al., xe2x80x9cTransponder Arrangementxe2x80x9d) describes a transponder arrangement comprising an interrogation unit which transmits at least one RF interrogation pulse to a responder unit which thereupon sends data stored therein back to the interrogation unit in the form of a modulated RF carrier.
The basic transponder concept has been refined and modified for specific applications. For instance, in the paper xe2x80x9cA Low Power Transponder IC for High Performance Identification Systemsxe2x80x9d (U. Kaiser and W. Steinhagen, 1994 Custom Integrated Circuits Conf., Proc. CICC ""94, pp. 14.4.1-14.4.4), an integrated circuit for a battery-less transponder system is presented. Battery-less transponders require contactless transmission of both the information and power between a mobile data carrier and a stationary or hand-held reader unit, allowing significant reading distance (about 2 m) due to separation of the powering and data transmission phases. First, energy is transmitted to and stored in a supply capacitor of the transponder. Second, the data information is then sent back to the reader unit using the energy stored in the capacitor.
Devices with these characteristics are for instance fabricated by Texas Instruments Incorporated under the tradename TIRIS(trademark). Applications for these transponders include identifications over a certain distance, or detection whether the object is at a predetermined location or not. In other examples, physical parameters such as the temperature or the pressure are to be interrogated directly at or in the object without direct access to the object being possible. The devices are robust and reliable under difficult environmental conditions (dust, humidity, heat, cold, etc.). The devices can for instance be attached to an animal which can then be identified at an interrogation point without direct contact, or to a person which can then obtain access to restricted areas. Other examples include computer-controlled industrial production for identifying objects marked by the transponder.
None of these capabilities include permanent storing or wireless retrieving of the chip""s individual identification, characteristics and performance. An approach to utilize the fuses of redundant rows and columns in dynamic random-access memories (DRAMs) for coding data, offers only very limited amounts of data, which further have to be retrieved through the device pins in complicated ways and cannot be retrieved at all when the device is active. When the device is mounted on a board, the stored information is no longer accessible.
In addition to the theft watch mentioned above, permanent individual chip identification is desired by recent requirements in qualification (e.g., ISO 9000). Furthermore, individual chip information regarding location within a semiconductor wafer, fabrication history, batch identification, and parametric and functional test results would greatly support recent efforts to achieve so-called xe2x80x9cbuilt-in reliabilityxe2x80x9d. This refers to chip reliability assured by painstaking adherence during chip fabrication to recognized design rules and process controlsxe2x80x94an approach much faster and cheaper than the traditional so-called xe2x80x9ctested-in reliabilityxe2x80x9d which is guaranteed only after prolonged and accelerated testing. Unfortunately, none of this information is available today for individual chips, or it can be obtained only after expensive efforts, such as the (destructive) removal of chip packages in order to access chips for time-consuming analysis.
An urgent need has therefore arisen for a low-cost and uncomplicated method to permanently tag each individual semiconductor chip, and an easily applicable, always available technique to read the stored information, while not interfering with device operation. Any solid-state structure required by the method should use configurations which are fully integrated in the circuit level of the chip but consume only minimal silicon real estate, and which can be fabricated without additional cost using the same mass-production processes as the actual circuit. The system and method should be applicable to a wide spectrum of design, material and process variations, leading to improved process yield and device reliability. Preferably, these innovations should be accomplished using the installed process and equipment base so that no investment in new manufacturing machines is needed.
The present invention is related to semiconductor integrated circuits (ICs) of any kind, especially those having high density and high value. These ICs can be found in many semiconductor device families such as processors, digital and analog devices, to memory and logic devices, high frequency and high power devices, specifically in large area chip categories. The invention offers an inexpensive way to permanently store into, and wireless retrieve from an integrated circuit chip a coded individual identification as well as manufacturing and engineering data. Examples include wafer fab lot number, chip location on the wafer, test results, bin number and so on.
Some of the major features of the invention to both the manufacturer and the user comprise:
Data storage and retrieval: Individual wafer level engineering data can be stored in the chip and then retrieved at any time, even after the chip has been encapsulated or packaged and assembled on a board. Consequently, parametric and functional performance data measured at the wafer level can be compared to final test data after assembly. This task has been recognized as a necessity in manufacturing science for cost-conscious process development, yet was unobtainable before the invention.
The comparison of design expectations and process results enables a stabilization of the process at its optimum and in a shorter time, thus shortening the number of design revisions customarily required to optimize a device design.
Anti-theft coding: Tagging the IC by the teachings of the invention, allows wireless identification of origin and source of the IC, even when it is already assembled into a finished product. The invention thus represents an effective aid for law enforcement.
Easy warehouse handling: With every single IC uniquely identified according to the invention, handling and shipping operations become easily automated and error-free, thus contributing to reduced costs and human errors.
Better customer service: Correlating with the wafer level engineering and manufacturing data encoded according to the invention, field failures of semiconductor devices can be more understood and eventually prevented. The invention offers the urgently needed advancement of improving product quality and reliability by process control, thus building-in reliability rather than testing it in.
As the invention teaches, these features will be realized without interfering with the layout and design of the IC, or its operating performance, or its specifications.
In accordance with the present invention, a small amount of IC real estate (less than 0.1% of an average IC area, or less than 1 bond pad area) is used to add a small IC as an information unit. This information unit is fabricated into the same surface of the semiconductor chip as the main IC, but represents an electrically separate entity. The information unit is fabricated concurrently with the main IC, and consequently requires no extra processing steps or cost for manufacturing. It contains an electronic data bank, made of a plurality of electrical fuses which can be irreversibly opened by laser pulses.
The information unit is powered wirelessly and continuously by radio-frequency signals, sent by an interrogation device and received by an antenna. This antenna is also integrated into the semiconductor chip and electrically connected to the information unit. This antenna is also fabricated concurrently with the main IC, requiring no extra processing steps or cost. The same antenna serves to broadcast the data stored in the data bank after the data have been used to modulate the received signals. The broadcast data are received by the interrogation device and forwarded to further analysis.
No extra component parts, such as an energy-storing capacitor or a separate antenna, are needed.
It is an object of the invention to tag semiconductor IC chips with individual information about identification, production history and performance, and to provide means to the chip to retrieve this information wirelessly. This object is achieved through integrating an information unit and an electrically connected antenna to the IC surface of the chip and keeping both electrically separate from the IC.
Another object of the present invention is to design the information unit so that the information can be encoded in a data bank while the chip is still in wafer form, as well as after its singulation. This object is achieved by providing a plurality of electrical fuses in the data bank which can be irreversibly opened by applying focused laser pulses.
Another object of the present invention is to provide fabrication processes for the information unit and the antenna which are concurrent to the IC fabrication processes, and also operate at high speed, so that they do not add extra cost to the manufacturing.
Another object of the present invention is to design the information unit and antenna such that their fabrication is flexible and can be adopted to the most commonly used and accepted IC fabrication processes.
Another object of the present invention is to provide the information unit with means to receive constant electromagnetic signals from an interrogation device through the antenna. Furthermore, the information unit comprises means to modulate the received signals by encoding wave forms from the electronic data stored in the data bank. After modulation, the antenna is enabled to respond the encoded information back to the cooperating interrogation device.
Another object of the present invention is to format the retrieved modulated signals such that they can be electronically processed, for instance by a tester or a data analyzer.
These objects have been achieved by the teachings of the invention concerning design concepts and process flows suitable for mass production. Various modifications have been successfully employed to satisfy different selections of product geometries and materials.
In one embodiment of the invention, the information unit is located in one corner of the semiconductor chip, integrated into the circuit surface, and the antenna is a closed metallized line, also integrated into the circuit surface of the chip, surrounding the IC.
In another embodiment of the invention, the antenna is part of the sacrificial metal structures positioned in proximity to the dicing lines surrounding the IC for arresting nascent microcracks.
In another embodiment of the invention, the parts of the information unitxe2x80x94the rectifier bridge circuit, the electronic clock extract circuit, the electronic encoder/modulator circuit, and the data bankxe2x80x94are spatially distributed in available niches of the IC, thus minimizing any real estate area consumed.
In yet another aspect of the invention, a method of fabricating the information unit includes the steps of forming an IC, concurrently forming the information unit by using certain steps of the IC process so that the information unit remains electrically separate from the IC, and concurrently the antenna by using certain steps of the IC process so that the antenna becomes electrically connected to the information unit.
In another aspect of the invention, laser pulses are applied in wafer form after multiprobe and/or after singulated chip assembly to open selected fuses and thus permanently encode electronic data.
In another aspect of the invention, a method of operating the information unit includes wireless and continuous powering by transmitting continuous interrogation signals from a cooperating interrogation device to the antenna. The interrogation signals are modulated by encoding wave forms from the electronic data stored in the data bank. Using again the antenna, the modulated signals are sent back to and received by the interrogation device.